Flow control valves are a well known and integral part of most irrigation systems. A typical example can be seen in U.S. Pat. No. 6,394,413 to Lohde, et al, herein incorporated by reference.
These valves control the flow of water through an upstream pipe and thereby turn sprinklers fed by the pipe on and off. Such valves are usually remotely actuated by control signals sent from an automated irrigation controller. Often, these control signals are electric impulses sent from the controller to a solenoid in the valve which ultimately controls whether the valve is open or closed.
Pilot-activated diaphragm-operated valves for use in irrigation systems are well known. One example can be seen in U.S. Pat. No. 3,336,843, herein incorporated by reference.
This style of valve has a closure member with a sealing surface which moves against or away from an annular seat to close or open the valve, respectively. Integral to the closure member is a diaphragm positioned to seal off an upper portion of the valve. When the valve is to be opened, the fluid pressure is relieved by bleeding fluid out of the diaphragm chamber through a manual valve or a remotely operated solenoid valve. Relieving this pressure allows the closure member to move upwards as water passes through the valve.
To save on manufacturing expenses and also to avoid the negative effects of material warpage and deformation, the closure member must be molded in such a way that it has a constant wall thickness, resulting in open channels or spaces, commonly called “material savers.” What has been discovered, however, is that over time, the diaphragm may extrude into these channels or spaces. This extrusion increases tension on the diaphragm, preventing valve closure at low water flows.
Some prior art valves available on the market today prevent the diaphragm extrusion into the closure member by providing a separate plastic insert into the inner channel of the guide washer. While this method prevents diaphragm extrusion, it presents increased manufacturing expense and difficulties by presenting another plastic part to design and injection mold. Further, the manufacturing conditions for both the closure member and the insert must be highly controlled and precise, otherwise the insert will fit poorly within the closure member, risking inefficient or faulty valve operation.
Therefore, what is needed is a single piece closure member that is easily manufactured, yet also prevents diaphragm extrusion within the closure member.